1. Field of the Invention
This invention relates to molding of concrete blocks and more especially to apparatus and methods for removing extraneous core mark material from molded concrete blocks.
2. Description of the Prior Art:
A popular type of concrete block is made with one or more core bars which form holes between two or more sections which are split apart after the block is cured to present a rough, cut stone surface appearance and vertical recesses, e.g., ribs or flutes, between areas of rough, split surface. Conventional concrete block units which are not split apart are also made by use of core bars. The core bar conventionally leaves what is called a core mark on the block immediately after molding as the block is withdrawn from the mold.
The core mark may be thought of as a ridge of concrete occurring on the top surface of a concrete masonary unit. The core mark occurs in the center of the web and the web may be thought of as being that portion of a concrete block which connects one face shell to the other and comprises a solid portion of the block between the hollow cores or openings in the block. The core mark in one operation in which the invention has been applied has been measured and has been found to be approximately 5/16 inch wide and 3/8 inch high for substantially the entire length of the block. Core mark material has also been observed as consisting of unpacked concrete which occurs under the bar which holds the cups or cylinders in place during the molding process. These cups or cylinders create the holes or hollow portions of the block.
Some concrete block units are split after being formed while other concrete block units are not designed to be split. A conventional block may be considered as a concrete masonary unit which is not to be split down the center line of the core and in the area where the core mark occurs. The split rib or splt flute-type block may be considered as a concrete masonary unit which after manufacture and curing is split along the center line of the unit and in line with the core mark. Such units are molded in siamese fashion and are later divided by the splitting process. Thus, they are spoken of in the trade as siamese units.
The splitting of a split rib or split flute-type block is accomplished by two vertically aligned blades moving simultaneously into the unit. One blade moves vertically upwardly into the bottom of the block and a second blade moves vertically downwardly into the top of the block. The blades operate in common vertical plane and are in a straight line over and under the center of the cores. The top blade splits through the rib or flute area and therefore splits through the core mark area associated with the rib or flute area. It is therefore necessary that the core mark be removed from the rib or flute area of siamese units. If the core marks are left in their original position in the rib or flute area of siamese units the top splitting blade will be caused to shift off center in the splitting operation and will thereby create two split units of uneven dimensions. It should also be remembered that siamese blocks also have conventional core marks associated with openings through which no splitting occurs.
It has been the practice to remove the conventional core mark not only because it was unsightly but primarily because the presence of such core mark created a difficult leveling situation when the mason attempted to lay the masonary unit in the wall. In the past this core mark was removed from the masonary unit while in a "green" or uncured state by a fiber brush arranged to sweep along the top surface of the block as the block was moved on a conveyor away from the molding machine. Another practice in the trade has been to remove the core mark by employing a tensioned steel wire placed across the path of the block and at a height which avoids scraping the block but is sufficiently close to the top surface of the block to clip the core mark as the block moves beneath the wire and away from the block molding machine on the conveyor.
The two kinds of apparatus and methods described above have proven to be generally satisfactory for removing core marks on conventional-type blocks. However, if the concrete masonary units are made in siamese for the purpose of splitting along the center line of the rib or flute associated core openings, it has been found necessary that the core marks be removed by an apparatus and method other than those which have been described. It is particularly necessary to remove such core mark material from siamese-type masonary units where the core holes associated with the ribs or flutes are small in size and thereby create a small slot between the ribs or flutes formed after splitting. If the core marks associated with siamese-type masonry units are removed from the rib or flute portion of the siamese units by either of the described prior art apparatus and methods, the loose, granulated concrete material resulting from the removal process tends to fall and lodge in the small openings associated with the rib or flute portions of the block and thus become an integral part of the masonry unit where the material happens to fall. Such extraneous material creates an irregular and unsightly situation when these siamese masonry units are later split. The importance of this undesirable situation to the trade can be appreciated by observing that the flutes or ribs of siamese units ultimately become decorative facings of buildings which employ the specialty siamese-types of masonry units. Thus, the presence of such extraneous core mark material in the rib or flute portions of siamese concrete block units have been of considerable concern to owners of buildings as well as to architects and to masonry contractors. Architects, for example, are beginning to insist on split masonry units being free of granulated concrete lodged between the ribs and flutes.
In order to deliver "clean" rib or flute siamese units, the more quality conscious concrete block manufacturers have in the past used a sharp, hoe-type rake to scrape the core marks from the rib or flute portions of the siamese units after such masonry units have been cured and split. Cured granulated concrete will not lodge in the small openings. However, the use of such scraping apparatus and method requires the use of an additional employee and has not proven to be entirely satisfactory in obtaining the desired clean appearance in the finished product.
Thus, it would be desirable to have an apparatus and method for removing core mark material from both conventional as well as siamese-type masonry units without involving manual labor and in a manner designed to prevent the core mark material from being cured and hardening on the block surfaces or between the ribs or flutes in the case of split siamese units. It would also be desirable in the case of split blocks to eliminate the unsightly appearance associated with hardened core mark material in the rib or flute areas and to eliminate the need for additional manual labor to remove such material once it has been cured and has hardened. It would also not only be desirable to have an apparatus and method for removing core mark material from both conventional as well as siamese masonry units but it would also be desirable to have such an apparatus and method which, with minor adjustment, could be employed for removing such core mark material from any of the numerous sizes and forms of conventional and siamese masonry units as found in the trade.